INA FASSBENDER/Anadolu Agency/Getty Images(DORTMUND, Germany) -- German authorities are investigating after three explosive devices, apparently hidden in shrubs, detonated near the bus of the Borussia Dortmund soccer team in western Germany.

One player was injured in the attack, Spanish defender Marc Bartra, who officials described as "seriously injured." Borussia Dortmund CEO Hans-Joachim Watzke said in a Facebook Live video that Bartra is being treated for hand and arm injuries, "but it's not in any way life-threatening."

The team was headed to their Champions League quarter-final match against AS Monaco when the devices went off near their hotel outside Dortmund.

The state prosecutor said a letter was found nearby claiming responsibility for the blasts, but authorities refused to disclose any details as the investigation is ongoing.

According to BBC, fans at Westfalenstadion were told to stay at the stadium until authorities said it was safe to leave. Monaco fans there reportedly chanted, "Dortmund!" in support of the opposing team. The stadium was later evacuated safely, BBC reports.